Vapor electric lamp



Aug- 1 1 R. E. PETERSON ETAL VAPOR ELECTRIC LAMP Filed May 13, 1953ATTORNEY Patented Aug. 1%, i258 ine VAPGR ELECTRIC LAP/KP Robert E.Peterson, Cedar Grove, Melvin C. Unglert,

Wyclrofi, and Edward A. .lenhins, Chester, N. 3., assignors toWestinghouse Electric Corporation, East Pittshurgh, Pm, a corporation oiPennsylvania Application May 13, 1953, Serial No. 354,713

3 Claims. (ill. 313-484) This invention relates to vapor electric lampsand for illustrative purposes is shown in a dual envelope colorcorrection lamp.

Lamps of the character indicated have an inner envelope and an outerenvelope, both of which are sealed with respect to the outer atmosphere.Within the inner envelope are appropriate electrodes for obtaining adischarge within a gaseous atmosphere across a path which is madeconductive by ion zation of a gas. The initial voltage recuired toinstigate ionization along the path mentioned would bemuch higher thanthe voltagerequired to maintain the discharge after ionization isoncepromoted. it is therefore common practice to provide a startingelectrode in proximity to one of the main electrodes and obtain adischarge therebetween to create the initial ionization. A highervoltage is applied across the main electrodes and consequently when theionization is instigated, the discharge transfers from the startingelectrode to the path between the main electrodes. in order to obtainemission, the main electrodes have an emissive material applied thereto,such as thorium. The thorium has a pronounced propensity to sputter andas a result the eflicient light producing life of lamps of thischaracter has been limited by blackening of the wall of the innerenvelope from the deposit of thorium thereon.

in its broad aspect, the present invention is directed to means forovercoming the objectionable blackening of the envelope wall fromsputtering of thorium.

Of similar nature, the invention proposes the increase of lightmaintenance during the life of the lamp.

Somewhat more specifically, the invention proposes confining thethoriated portion of the electrode so as to intercept the sputteredthorium and keep it from reaching the light transmitting portion of theenvelope.

A further object of the invention is to position the thoriated portionof the electrode at a greater distance from the light transmittingportion of the envelope than the arc-striking portion of the mainelectrode.

A further object of the invention is to provide an appropriate shield inclose proximity to the thoriated portion of the electrode.

A further object of the invention is to catch the sputtered thorium at apart of the envelope where it may condense and deposit withoutdeleterious efiect and by means obtaining maximum interception of thesputtered material.

Still another object of the invention is to provide a structure enablinguse of quartz glass for the shield and at a location enabling a tightseal to be made therewith by the glass constituting the lighttransmitting portion of the envelope.

An additional object of the invention is to provide a structure whereinthe shield is relatively cool so that none of the sputtered materialwill be driven onto the light transmitting portion of the wall of theenvelope.

Other objects and advantages of the invention will appear to personsskilled in the art to which it appertains as the description proceeds,both by direct reference thereto and by implication from the context.

Referring to the accompanying drawing, in which like numerals ofreference indicate similar parts throughout the several views:

Figure 1 is an elevation of a dual envelope color correction lamp,wherein our invention is utilized;

Figure 2 is a longitudinal sectional view of the inner envelope andshowing the electrodes therein;

Figures 3 and 4 are cross-sectional views, taken on lines llllll andlVIV respectively, of Figure 2; and

Figure 5 is a longitudinal sectional view of a modified construction ofinner envelope and electrode.

in the specific embodiment of the invention illustrated in said drawing,and first considering the embodiment of our invention illustrated inFigs. 1 to 4, there is shown a color-corrected high pressure mercuryvapor lamp 11, comprising a quartz inner envelope 12, the ends of whichare supported by metal plates 13 and 14, through which pass supportingwires 15 and 16, welded to a lead-in 1'7 projecting from press 19,adjacent the base 21 of the outer bulb 22.

The lamp 11 has a main electrode 25 at its outer end connected tosupport wire 15 by a transversal 2s, and a main electrode 27 at itsinner end connected to lead 1 5 by flexible conductor 28. A startingelectrode 2? is provided, connected through a resistor St) to lead 17.The envelope 1?. encloses a quantity of mercury and inert gas at apresure such that it is normally below atmospheric, but will be aboveatmospheric when the lamp is in operation, as is customary in lamps ofthis character.

The outer envelope 22, in the persent embodiment, is generallyellipsoidal with its long axis, coaxial with that of the inner envelope12, so that the lamp will operate as nearly isothermally as possible.The outer end portion 31, however, opposite the base 21, as well as theneck portion 32, are formed generally cylindrical about the uis of theenvelope l2 and of a relatively small diameter, so as to be engaged byspring fingers 33 on the supporting wires 15 and 16 for positioning saidenvelope 12 in the outer envelope 22. The space between th envelopes l2and 22 is evacuated, if desired, or may be filled with inert atmosphere.The inner surface or the outer envelope 22 is coated with a selectedcolor-correcting phosphor 34. For an approximate optimum operatingtemperature of the phosphor 34, assuming the phosphor to be thepreferred magnesium fiuorogermanate, the length of the ellipsodialportion of the bulb 22, when enclosing a 400 watt lamp, is about 8", andits maximum transverse dimension is about 6".

The general organization described above and appropriate phosphors andmethod of applying the same are described in greater detail in priorapplications Serial No. 126,506, filed November 10, 1949, in the name ofLuke Thorington, now U. S. Patent No. 2,748,303, dated May 29, 1956, andSerial No. 244,344, filed August 30, 1951, in the names of George H.Lockwood and Robert E. Peterson, now U. S. Patent No. 2,707,687, datedMay 3, 1955, both being assigned to the same assignee as the presentapplication.

The present invention inheres more particularly in the constructionofinner envelope 12 and the electrodes therein. Sufiice it to say, forpurposes of the present invention, that the outer envelope 22 has aninner coating of phosphor which is affected by the light from the innerenvelope and gives a desired color-corrected light exterior to the outerenvelope.

As described above and also indicated in the abovenoted patents, theinner envelope provides two main electrodes at opposite ends of theenvelope and each of these electrodes has a coil 35 thereon andpreferably includes thorium between the coil and the electrode, the coilserving to some extent to confine sputtering of the thorium. In thepatents referred to the thoriated portions of the electrodes are shownnext to the ends of the electrodes thatare directed toward each'lotherand which, for convenience, will be herein referred to as the innerendsof said electrodes. present invention is to locate thethoriatedportion of each of these main electrodes as remote from eachother as possible and spaced rearwardly from said inner ends of the mainelectrodes. Preferably, the thoriated portion is at a distance back fromthe op'enend of the shield greater than radial distance between theelectrode and shield. V w o In addition to the foregoin g feature, thepresent invention contemplatesshielding the thoriated portion of theelectrode inapart of the envelope not required for light transmittingpurposes, but at the same time locating the inner ends of the mainelectrodes within the light transmitting portion of the-envelope.According to the showing in Figs. 1 to 4, the mid-section 36 of theinner envelope has a larger diameter than end portions 37, and said endportions 37 constitute the shields referred to above. The thoriatedportion'of the main electrodes are Well within andrrelativelyl close tothe closed ends of the shield portions 37 and at a considerable distancefrom the transition or junction between the shield portion and thelighttransmittingor mid-portion of the envelope. In view of the factthat the electrodes are thus relatively close to the shield portions ofthe envelope, the heat radiating from the electrode is severe on theshield portion of the envelope, and it consequently is necessary toutilize quartz glass or another heat resisting ceramic to constitute theshield. A structure is therefore required enablingtheuse of such amaterial for the shield and 'at the same time enabling it .to be sealedvacuum-tight to the light transmitting portion of the envelope. As.shown in Figs. 1 to 4, inclusive, this desideratum is accomplished veryconveniently'by the construction above described with the utilization ofreduced diameter end portions 37 for the envelope projecting Anessential feature of the axially from the ends of the light transmittingportion 36 of the envelope, enabling the sealto be accessible duringfabrication at'the exterior of both the large and small portionsoftheenvelope.v Beyond the shield portion at each end of the envelope, theglass thereat is formed into a press 38 which seals the respectivelead-in wires vacuum-tight through the compressed glass. Accordingto thepresent showing, the particular seal is made, by utilization of a fiatsection 39 in the lead-in connection which is flatwise with respect tothe flattened faces of the press to obtain a leak proof seal thereat;

It may be pointed out that the starting electrode 29 is likewise wellwithin one of the shields and that the initiating electron dischargefrom theadjacent thoriated portion of themain electrode is at a distancewell below the junction between the shield and the light transmittingportion of the envelope. According to the present showing, the reducedor shield portion 37 of the envelope is not required for lighttransmitting purposes as the discharge is-between the ends of the mainelectrodes and therefore within the larger or light transmittingportion36 of the envelope. The shield is relatively close to the thoriatedportion of the main electrode and much longer than said portion sothatthe sputtering of thorium will be quickly intercepted by the shieldas a result of which the sputtering will not extend into the lighttransmitting portion of the envelope. Therefore said envelopewill remainsubstantially free from any such sputtering of the thorium throughoutthe life of the lamp, whereas heretofore the usefulness of the lamp wasimpaired by the blackening ofthe light transmitting portion and the'bl'ackeningwas under those conditions a limiting factor as to the -lifeof the lamp.

has its outer or far end joined or sealed to the end of the envelope 36arather than to the rear or inner end as in the other figures.Consequently, in Fig. 5 the shield 3711 projects into the envelope 36ainstead of projecting outwardly, but in both instances, the shield iscoaxial with the envelope, the 'main electrode 25 or 27 projects fromthe shield within the envelope and the light-transmitting portion of theenvelope is that part thereof in the region defined by the spacingbetween the opposed iinier ends of the shields. Furthermore, in eitherconstruction the inward ends of the electrodes 25,27 may have a knoborenlargement 40, if so desired, to better withstand erosive effects ofthe arc thereat. Likewise, in both forms of the invention hereindisclosed, the thoriated portion of the main electrode is deep in theshield, thus effecting a recessed positioning of the emissive materialand providing a shield which is relatively close to the emissive areafor prompt interception of sputtered material and for keeping thelighhtransmitting portion of the envelope clear of sputtered materials.

We claim:

l. A high pressure discharge'lamp having an envelope with alight-transmitting portion and an integrally-formed constricted portionco-axially disposed at each end thereof, said constricted portions eachhaving an end open to the interior of said envelope, an electrode sealedin each end of said envelope and extending longitudinally through saidconstricted portions into said envelope, each of said electrodeshavingan arcesupporting portion and an electron-emissive portion-remotefrom said arc-supporting portion, said electrode arc-supporting portionsprojecting into said envelope light-transmitting portion a substantialdistance beyond the open ends of said constricted portions of saidenvelope to serve as discharge terminals and define a discharge path,and said electrode electron-emissive portions disposed outwardly fromsaid electrode arcsupporting portions entirely within the saidconstricted portions of the envelope and more remote from the open endsthereof than the radial distance between said constricted portions andsaid electrodes whereby substantially all the sputteredelectron-emissivematerial isintercepted by and deposited onthe saidconstricted portions of the envelope during the operation of said lamp.7

2. A highpressure discharge lamp having a tubular envelope withalight-transmitting portion and an endclosing and integrally-formedconstricted portion coaxially disposed at each end thereof, an electrodesealed in each of. said'constricted end-closing portions and extendinglongitudinally into said envelope, each of said electrodes having'anarc-supporting portion and an electronemissive portion remote from saidarc-supporting portion, said electrode arc-supporting portionsprojecting into said envelope light-transmitting portion a substantialdistance beyond the said constricted end-closing portions of saidenvelope to serve as discharge terminals and define a dischargepath, andsaid electrode electron-emissive portions disposed outwardly from saidelectrode arc-supporting portions entirely within said constricted.endclosing portions of theenvelope and more remote from the juncturesthereof with the said envelope light-transmitting portion than theradial distance between said eonstricted end-closing portions and saidelectrodes whereby substantially all the sputtered electron-emissivematerial is intercepted by and deposited on the said constrictedend-closing portions of the envelope during the operation of said lamp.

3. A high pressure discharge lamp having an envelope with alight-transmitting portion and an integrally-formed constricted portionco-axially disposed at each end thereof, each of said constrictedportions protruding into. said light-transmitting portion and having anend open to the interior of said envelope, anelectrode sealed in each'of saidconstricted portions and. extending longitudinally through saidconstricted portions into said envelope, each K a of said electrodeshaving an arc-supporting portion and an electron-emissive portion remotefrom said arc-supporting portion, said electrode arc-supporting portionsprojecting into said envelope light-transmitting portion a substantialdistance beyond the open ends of said constricted portions of saidenvelope to serve as discharge terminals and define a discharge path,and said electrode electron-emissive portions disposed outwardly fromsaid electrode arc-supporting portions entirely within the saidconstricted portions of the envelope and more remote from the open endsthereof than the radial distance between said constricted portions andsaid electrodes where- References Cited in the file of this patentUNITED STATES PATENTS 2,007,947 Braselton July 9, 1935 2,116,429Gooskens May 3, 1938 2,177,714 Hagen Oct. 31, 1939 2,453,118 BuckinghamNov. 9, 1948

